Answer
$80$ $J$
Work Step by Step
Along abc, the change in internal energy is $160$ $J$ (because the change in internal enegry across the entire cycle is 0 and the change along ca is -160) and the heat transferred is $200+40=240$ $J$. Using the first law of thermo, $Q-W = \Delta U, 240-W = 160, W = 80$ $J$.